1. Field of the Invention
The present invention relates to a belt hoist wherein a winding member for winding a belt thereon is rotationally supported between a pair of opposing side plates.
2. Description of the Prior Art
Belt hoists of this kind are known as disclosed by Japanese Laid-Open Utility Model Publications No. Hei 6(1994)-25290 and No. Hei 5(1993)-32386, for example. The belt hoists disclosed by these publications are so structured that a flat belt retaining a hook or equivalent at its front end portion is wound around the winding member rotationally driven by a normal and reverse rotation motor. The belt is taken up on or paid out from the winding member to hoist up and down or drag a load through the belt.
Further, the belt hoist disclosed by the Japanese Laid-Open Utility Model Publications No. Hei 5(1993)-32386 is so structured that parts to be detected are fitted to the belt at several points along a lengthwise direction thereof and an overwinding detecting sensor and an over-lowering detecting sensor are retained to a fixed member of the hoist with spacing from the belt at a specified interval to be opposite to the parts to be detected at the time of the overwinding and over-lowering of the belt. When the respective sensors are opposite to the related parts to be detected, rotation of the motor is stopped according to the output from the sensors to prevent the overwinding of the belt.
This constructed belt hoist of conventional type has the advantage that various kinds of components of the hoist can be prevented from breakage resulting from the overwinding of the belt at the time of hoisting up and down or dragging a load through the belt, but it has disadvantages that parts count increases and thus structure is complicated, due to the structure that the parts to be detected are provided at several points of the belt and the sensors are provided at the fixed member. In addition, since this conventional type belt hoist has no means for preventing the belt from being taken up with twisted, the belt may sometimes be coiled randomly.